In 1990 he was jailed for 10 years for a jewellery raid while armed with a sawn-off shotgun. In April 1999, he was sentenced to eight years for five robberies.

His previous life term, with a minimum tariff of five-and-a-half years, was imposed in April 2006 at Wood Green Crown Court for four robberies in Stoke Newington, north London, and possessing an imitation firearm.

He had been released and was on licence when he committed the latest offences.

After being told Sanderson was previously given life, Judge Martin Joy asked at an earlier hearing: "How come he is free?"

Andrew Espley, defending, said a second life sentence would be "an exercise in futility", as Sanderson would only be released if the Home Secretary decided it was safe to do so.

"I submit that given the nature of this offence was not as severe as the previous ones when you look at it in the round, there is no need to impose a sentence of imprisonment for life," he said.

"This is not so serious that only life can be justified. Mercifully, the victim is a woman of fortitude who has expressed that she has put this behind her. It is worth pointing out nobody got hurt."

Mr Espley added: "Things were going well for him. This is very odd indeed."

Judge Martin Joy sits at Maidstone Crown Court

Passing sentence, Judge Joy said: "There are factors here which take it to the highest level. This was a robbery of a small business in a High Street.

"Such businesses should be able to look to the protection of the court, particularly where weapons are used. I am entirely satisfied this defendant is dangerous.

"He has carried out yet another armed robbery. It must be life imprisonment. I have to recognise the public will be concerned as to exactly what a life sentence does mean."

The judge added that had he imposed a determinate sentence of 10 years, Sanderson would have been entitled to be released when he had served half.

DC Tony Hatcher, from Kent Police, said: "This is a good result which means someone who was a very serious threat to the public has now been taken off the streets.

"Although Sanderson could be eligible for parole in five years he will have to clearly demonstrate that he no longer presents a danger to the public before there is any chance of him being released.

"There is every possibility that Sanderson will remain in prison for a very long time."